Embodiments of the present invention relate to a bore selector, and more specifically, to a bore selector being used for coupling a monobore riser to a dual bore subsea installation.
Development within offshore oil and gas exploration in the recent years has been directed to subsea installations for processing and transport of oil and gas. The subsea installation is located at the well on the seabed and is connected to a floating structure or platform by means of a so-called riser, which constitutes a conduit between the subsea installation and the floating structure or platform. The subsea installation may be a wellhead or other type of equipment positioned on the seabed or in a fixed position above the seabed. The floating structure may for instance be a vessel.
A riser may be of the monobore type or the dual bore type. A dual bore riser comprises a production pipe and an annulus pipe extending in parallel with the production pipe. A monobore riser comprises a production pipe but no annulus pipe. A monobore riser is safer and easier to handle than a dual bore riser. Furthermore, the costs associated with the manufacturing and use of a monobore riser are substantially lower as compared to a dual bore riser. Thus, the use of a monobore riser is often preferable, particularly when the riser is to be used at great sea depths. When a monobore riser is used for operations on a dual bore subsea installation it is favorable to use a bore selector, which makes it possible to selectively connect the monobore riser to the production bore or the annulus bore of the subsea installation. Different types of such bore selectors are for instance disclosed in U.S. Pat. Nos. 5,377,762A, 6,170,578B1 and GB2258675A.